1. Field of the Invention
THIS INVENTION RELATES to a pressure regulator, particularly suitable for use as a breathing demand valve system, in, for example, diving, rescue, escape and resuscitation equipment.
There are many cases in which the need to breathe depends upon a source of air, or other breathable gas, stored at a high pressure in a cylinder or bottle. The specific storage pressures of such gases varies according to the nature of the gas and the particular application but, as a general rule, the stored gas pressure may vary between 1,800 psi (1.2xc3x97107 Pa) and 4,500 psi (3.1xc3x97107 Pa). In order to bring the stored gas pressure to a useable level, a high pressure regulator is usually mounted on the cylinder to provide an output (set) pressure of the order of 60-105 psi (4.1xc3x97105-7.2xc3x97105 Pa), dependant upon the application and the particular manufacturer""s design. The medium level output from the high pressure, or first stage, unit is applied to some form of breathing valve system.
2. Description of the Related Art
Such a breathing valve system, or demand valve, may be provided with a diaphragm, which typically actuates some form of inlet valve to allow flow of the medium level gas pressure, supplied from the high pressure regulator, to the mouth of the user. The inlet valve in many established designs is an unbalanced poppet valve, which is held closed against the supply pressure through the action of a light spring and is opened by deflection of the diaphragm acting against the spring. Conventionally, in order to obtain power gain from this design form, a long lever is employed to operate the inlet valve, transmitting the thrust due to the deflection of the diaphragm. Known variations include manual adjustment of the valve aperture and/or opening pressure, to suit different operating requirements or conditions.
A disadvantage of the lever actuating design described above is that, due to inevitable manufacturing tolerance variations in the various components, some selective assembly and adjustments are necessary in order to tune the function of the valve unit so as to be within acceptable performance limits.
GB 2298026 discloses an alternative arrangement for a breathing valve system, in which the inlet valve is in a pressure balanced module. The module incorporates an inlet poppet valve which is as nearly perfectly balanced as is reasonable under good quality manufacturing tolerances and conditions, so that the poppet valve can be opened directly by the thrust due to the deflection of a suitably sized diaphragm, without the need for any form of lever arrangement.
In the arrangement of GB 2298026, in order to actuate the opening of the inlet valve directly, the diaphragm is positioned opposite, and faces, the inlet valve such that, upon deflection, the diaphragm is urged against the stem of the inlet poppet valve so as to move the stem axially and consequently open the valve. Accordingly, when the valve is in an open position, a portion of the pressurised fluid flow through the valve impinges upon the underside of the diaphragm, tending to deflect the diaphragm in a direction away from the end of the poppet valve stem and thus tending to close the inlet valve, so that there is a negative feedback effect. For certain applications such as, for example, diving, there is a requirement for a relatively high maximum inhalation gas flow, with a predetermined inhalation suction, such that the negative feedback effect described above is considerable, and a point may be reached whereby no matter how much suction force is applied to the diaphragm, virtually no change in the mass gas flow delivered to the user can take place. This is because the higher the gas flow through the inlet valve, the greater the reaction force on the diaphragm tending to close of the inlet valve and reduce the mass gas flow.
It is an object of the present invention to provide a demand valve system which mitigates the self-limiting pressure problem described above
According to one aspect of the present invention, there is provided a pressure regulator suitable for use as a breathing demand valve in various self-contained breathing apparatus, comprising a first chamber having an inlet port, the inlet port being connectable to the outlet of a pressurised fluid supply, an inlet valve being positioned within the inlet port and biased so as to seal the first chamber from the pressurised fluid supply, wherein the opening of the inlet valve can be actuated by the thrust due to the deflection of a diaphragm positioned so as to separate the first chamber from a second chamber, a baffle plate positioned in between the diaphragm and inlet port reducing negative feedback to the flow rate through the first chamber by preventing a portion of the pressurised fluid flow released through the open inlet valve from impinging upon, and consequently deflecting, the diaphragm in a direction tending to close the inlet valve.
For low pressure valve applications, it is known to provide breathing valve systems which employ a convoluted diaphragm. The active part of the diaphragm can be made relatively thin and flexible, making for a sensitive diaphragm which is essential for an accurate, low pressure demand valve. The use of a convoluted diaphragm has the additional advantage that, unlike a flat-type diaphragm, the effective area of a convoluted diaphragm is readily calculable, and is constant throughout its working range of movement. This feature provides functional predictability, which is essential for low pressure regulator applications.
A problem in the use of diaphragms in any breathing demand valve application, and particularly where sensitive diaphragms are used, such as convoluted diaphragms, is that of providing a means of clamping and sealing the peripheral sealing flange of the diaphragm, without subjecting the diaphragm to the effects of stress displacement likely to cause material distortion within the diaphragm body.
Conventionally, the sealing flange is merely clamped between two surfaces. In a known development, one or both of the clamping surfaces may be provided with a series of annular grooves, into which flows some of the elastomeric material which forms the flange region of the diaphragm. The flow of material into these grooves serves to grip the flange region of the diaphragm and increases the degree of sealing around the periphery of the diaphragm. However, the grooves only take up a proportion of the elastomeric flow in the flange region of the diaphragm and the remainder of the flow of elastomeric material, caused by the clamping, is into the main body of the diaphragm, which may distort the body of the diaphragm and compromise the sensitivity in the response of the diaphragm.
It is a further object of the present invention to provide a demand valve system employing a diaphragm, means being provided to clamp the diaphragm while providing a substantial reduction in the transferral of the effects of stress displacement into the diaphragm, and consequent material distortion therein.
According to another aspect of the present invention there is provided a pressure regulator suitable for use as a breathing demand valve in various self-contained breathing apparatus, comprising a primary chamber and a convoluted diaphragm, the diaphragm being mounted within the primary chamber so as to provide a fluid tight seal around the diaphragm rim, while isolating the convoluted section of the diaphragm from distortion effects due to rim clamping or sealing forces.